The majority of present day integrated circuits (ICs) are implemented by using a plurality of interconnected field effect transistors (FETs), also called metal oxide semiconductor field effect transistors (MOSFETs or MOS transistors). The ICs are usually formed using both P-channel and N-channel FETs in which case the IC is referred to as a complementary MOS or CMOS IC. There is a continuing trend to incorporate more circuitry having greater complexity on a single IC chip. To continue this trend, the size of each individual device in the circuit and the spacing between device elements, or the pitch, are reduced for each new technology generation. Further, as the pitch is scaled to smaller dimensions, the thickness of gate insulators and electrodes used in the gate stacks of these devices is also reduced.
It is well known that the performance of a transistor device can be improved by applying an appropriate stress to the channel region to enhance the mobility of majority carriers. For example, the mobility of electrons, the majority carrier in an N-channel MOS (NMOS) transistor can be increased by applying a tensile longitudinal stress to the channel. Similarly, the mobility of holes, the majority carrier in a P-channel MOS (PMOS) transistor, can be increased by applying a compressive longitudinal channel stress. Tensile and compressive stress liner films have been incorporated as channel stress-inducing layers for both NMOS and PMOS devices, respectively, for the 65 nm, 45 nm, and 32 nm technology generations. However, because the thickness of these films decreases with device pitch, the stress applied, and thus the performance benefit achieved, also declines with each new generation. Further, as the thickness of gate stacks is reduced in advanced devices, the likelihood of channel contamination by impurity dopants from high energy ion implantation processes is increased.
Accordingly, it is desirable to provide methods for fabricating MOS devices having epitaxially-grown, stress-inducing source and drain regions. In addition, it is desirable to provide methods for epitaxially growing stress-induced source and drain regions using fewer process steps. Further, is it also desirable to provide such methods that alleviate the need to use ion implantation as a means of doping source and drain regions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.